DE3026374C2 - Spark plug with resistance glass seal - Google Patents

Description

The invention relates to a spark plug with resistance glass seal in the preamble of Claim 1 presupposed type Such a spark plug is to suppress the spark discharge generated interference signals effective.

Noise signals caused by interfered motor vehicle communication waves arise primarily at the spark plugs. In order to reduce such spurious signals, it is known that spark plugs with a built-in resistor are effective in this regard, as described in US Pat. Nos. 3,567,658 and 3,577,355 by forming part of the center electrode of the spark plug using a mixture of glass and electrically conductive powders to have a built-in resistance and forming an airtight seal between the center electrode and the insulator center bore. The composition of the electrically conductive glass seals on the side of the screw head and on the side of the center electrode of conventional resistance glass seal spark plugs mostly consists of electrically conductive metal powders, such as e.g. B. copper powder, and borosilicate glass, and the composition of the resistance glass seal arranged between the aforementioned electrically conductive glass seals generally consists of carbon, silicon carbide, glass and a filler. However, these known resistive glass seal spark plugs have disadvantages in that they have a higher coefficient of voltage of resistance (VCR) and are of a relatively small amount of noise reduction. The reasons for increasing the VCR value have been investigated, and it has been found that when the center electrode is airtightly sealed by heating a glass sealing material at high temperatures and hot-pressing it, a high resistance layer at the contact part between the electrically conductive glass sealing layer on the side of the screw head and the resistance glass sealing layer can be formed as a result of the flow of the glass sealing material and that this high resistance layer has a higher proportional voltage when a high voltage is applied to it, and that, since the electrically conductive glass seal on the side of the screw head penetrates the resistance glass sealing layer, its length due to the Adjacent the electrically conductive glass seal on the side of the screw head is significantly shortened to the side of the center electrode and the field strength per unit length that is applied to the resistor is greater. Further, it has been found that as the amount of silicon carbide to be added to the resistive glass sealing layer increases, the VCR also increases.

ψ These relationships also apply to a spark plug of the type presupposed at the beginning, which is derived from US-PS

K 24 59 282 is known; thereafter the electrically conductive glass seals consist of a mixture of

| ij preferably 55 parts of copper powder and 45 parts of borosilicate glass or lead-borosilicate glass and 3 parts of binding agent

{ so medium, while the resistance glass seal in between consists of preferably 62.4% borosilicate glass, 25.2% flux gap, 7.8% magnesium borate glass and 4.6% carbon. A similar spark plug is known from US Pat. No. 3,538,021.

On the other hand, US-PS 21 06 578 describes a spark plug with an electrically conductive glass seal

the center electrode, with the glass seal also containing carbon and possibly metal in addition to glass. One

additional resistance glass seal is not provided, so that the problem of occurrence mentioned

) an unfavorable high resistance layer between an electrically conductive glass seal and a

Resistance glass sealing does not occur here.

The invention is based on the object of developing a spark plug with a resistance glass seal of the type mentioned at the beginning with a low voltage coefficient of resistance (VCR) and stable properties, with hardly any high resistance layer appearing on the contact parts between the electrically conductive glass seals and the resistance glass seal in the course of manufacture .

According to the invention, this object is achieved by the characterizing features of claim 1. The spark plug according to the invention has, thanks to the carbon content, one or each electrical conductive glass seal has a low voltage coefficient of resistance and stable properties and is effective in reducing the level of interference from an ignition system.

A preferred embodiment of the invention is characterized in claim 2. For a better understanding of the invention, it is appropriate here to begin with a conventional resistance glass sealing spark plug to be explained according to the structure and composition of the sealing materials. this

happens in the following with reference to Fig. 1:

At the upper end of the screw head 1, a connection 2 is formed to which an electrical voltage can be applied, and at the lower end of the aluminum oxide insulator 7, a center electrode 3 is formed between the screw head 1 and the center electrode 3 are an electrically conductive glass seal 4 on the side of the Screw head, a resistance glass seal 5 and an electrically conductive glass seal 6 on the side the center electrode 3 is provided. The screw head 1 is surrounded by the aluminum oxide insulator 7, in which In the middle, an insulator center bore 8 is formed in which the center electrode 3, the individual seals 6.5 and 4 and the screw head 1 are arranged. The aluminum oxide insulator 7 is in an outer jacket 10 housed, which carries a grounding electrode 9 at its lower end The Miltelelectrode 3 and the Grounding electrodes 9 form a pair of discharge electrodes.

Such a resistive glass seal spark plug is generally made by having the center electrode 3 arranged in the central bore 8 of the aluminum oxide insulator 7, then the electrically conductive Glass seal 6 on the side of the center electrode, the resistance glass seal 5 and the electrically conductive one Glass seal 4 on the side of the screw head 1 fills the screw head 1 on the glass seal 4 arranges, the whole unit is heated in an oven and the screw head 1 down into the central bore 8 drives in under the application of pressure and at the same time the glass seal of the inner part of the central bore 8 causes The structure thus formed, containing the center electrode 3, is in the outer jacket 10 with the Ground electrode 9 arranged

The compositions of both the electrically conductive glass seal 4 on the side of the screw head 1 as well as the electrically conductive glass seal 6 on the side of the center electrode 3 of the known resistance glass seal spark plugs in most cases contain a metal in addition to the glass, and the composition the resistance glass seal 5 contains in most cases carbon, silicon carbide, glass and a filler.

An example of the manufacture of a conventional resistive glass sealing spark plug is shown below given:

An electrically conductive glass sealing material is made by adding 0.3 parts by weight of polyvinyl alcohol (PVA) to a mixture of 50 parts by weight of borosilicate glass powder and 50 parts by weight of finely powdered copper. A resistance glass sealing material is prepared by adding 0.3 parts by weight of PVA to a mixture of 70.5 parts by weight of borosilicate glass powders, 4.5 parts by weight of carbon powders, 20 parts by weight of silicon carbide powders and 5 parts by weight of alumina powders. After placing a center electrode 3 in the center hole 8 of an aluminum oxide insulator 7 for spark plugs, 0.1 g of the electrically conductive glass sealing material is filled in the center hole, 0.35 g of the resistance glass sealing material is filled thereon, 0.25 g of the electrically conductive glass sealing material is filled thereon, and finally a screw head 1 is placed thereon. The whole unit is placed in a furnace and heated to 85O ⁰ C and allowed pressure on the screw head act to force it down into the central bore. The resulting assembly is allowed to stand to cool and is placed in an outer shell 10 to obtain a finished resistance glass sealing spark plug.

The resistance glass sealing spark plugs produced in this way (130 in number) have initial resistance values (Ra) of 2.5 to 7.2 kn, VCR values of -80 ppm / V (ppm, ie proportion per 1 million parts) at 10 kV As mentioned above, the conventional resistor glass seal type spark plugs have disadvantages in that the resistance-voltage coefficient (VCR) is large and the amount of noise level reduction is small. In this connection, it has been found that the VCR value increases in the following cases:

(1) A high resistance layer that is slightly attached to the contact part between the electrically conductive glass seal 4 on the side of the screw head 1 and the resistance glass seal 5 due to the flow of the Glass sealing material at the time of heating the glass sealing material to a high temperature and the hot press of which can be formed to airtightly seal the center electrode 3, FIG larger partial voltage in the case of applying a high voltage thereto;

(2) the length of the resistive glass seal is due to the proximity of the electrically conductive glass seal 4 on the side of the screw head 1 and the electrically conductive glass seal 6 on the side of the Center electrode 3 as a result of the penetration of the electrically conductive glass seal 4 into the resistance glass seal 5 is much shorter, and the field strength per unit length that is applied to the resistor increases; and

(3) the amount of silicon carbide added is large.

Various attempts have been made to overcome these drawbacks. As a result, the following became Facts established: When fine powders of carbon, which are of poor wettability for glass in the Compared to a metal powder and has good electrical conductivity, at least that of electrical Conductive glass sealing material will be added to the side of the screw head on the contact part between the electrically conductive glass seal 4 on the side of the screw head and the resistance glass seal 5 no high resistance layer is produced. The reason for this is that the electrically conductive Glass seal 4 on the side of the screw head does not penetrate ie resistance glass seal 5, what leads to the fact that the effective length of the resistance glass seal 5 is significantly greater; also lets The VCA value improves as the proportion of carbide in the resistance glass sealing material decreases will.

Embodiments of the invention are explained in detail below, FIG. 1 in their external appearance of course also corresponds to the subject of the invention for which the fully extended

Line in FIG. 2 illustrates the interference field behavior, which is improved in comparison to the known.

Forty resistance glass sealing spark plugs for each sample (Sample Nos. 1 to 6) were prepared using the above-mentioned known method and using electrically conductive glass sealing materials as shown in Table 1 to form the electrically conductive glass seals 4 and 6 in Fig. 1 and the conventional resistive glass sealing materials mentioned above. The average VCR of these resistive glass seal spark plugs is shown in Table 1.

VCR was obtained from the following equation:

10 ⁶

R _L

V _H -V _L

(ppm / V),

where Rl means a resistance at a low voltage Vl (e.g. 4.5 V) and Rh means a resistance at a high voltage Vh (e.g. 10 kV).

As is clear from Table 1, when carbon is added to the electroconductive glass sealing material , the VCR value can be reduced considerably as compared with the case of using no carbon (-80 ppm / V) as mentioned above.

Table 1

Sample Composition of the electrically conductive glass sealing material

No. (Parts by weight)

Carbon copper glass iron

Brass

VCR

(ppm / V)

5 10 20 15 10 10

45 40 20 25

50 50 60 60 50 50

40

-60 -51 -53 -50 -53 -52

Forty resistance glass seal spark plugs for each sample (Sample Nos. 7 to 13) were used of the conventional method and using those shown in Table 2 electrically conductive glass sealing materials for forming the electrically conductive glass seals 4 and 6 and one Resistance glass sealing material produced by adding 0.3 parts by weight of PVA to a mixture of 90.7 parts by weight of borosilicate glass powders, 4.3 parts by weight of carbon powders and 5 parts by weight of silicon carbide powders. The average VCT? Of these resistance glass seal spark plugs is given in Table 2.

Table 2

Sample Composition of the electrically conductive glass sealing material

No. (Parts by weight)

Carbon copper glass iron

Brass

VCR (ppm / V)

7th 5 45 50 8th 10 40 50 9 20th 20th 60 10 15th 25th 60 11th - 50 50 12th 10 - 50 13th 10 50

40

-40 -33 -35 -34 -66 -31 -32

Forty resistance glass seal spark plugs for each sample (Sample Nos. 14 through 21) were used of the conventional method and using those shown in Table 3 electrically conductive glass sealing materials for forming the electrically conductive glass seals 4 and 6 and one Resistance glass sealing material produced by adding 0.3 parts by weight of PVA to a mixture of 85.6 parts by weight of borosilicate glass powders, 4.4 parts by weight of carbon powders and 10 parts by weight of silicon carbide powders. The average VCA of these resistance glass seal spark plugs is given in Table 3.

Table 3

Sample No.

Composition of the electrically conductive glass sealing material (parts by weight)

Carbon copper glass brass

iron

nickel

5 10

45 40

50 50

VCR

(ppm / V)

-46 -41

(Continuation)

Sample Composition of the electrically conductive glass sealing material No. (Parts by weight)

Carbon copper. Glass brass

iron

nickel

VCR (ppm / V)

15 20

10 10 10

25 20 50

60 60 50 50 50 50

40

40

-43 -47 -74 -41 -42 -41

Forty resistance glass seal spark plugs for each sample (Sample Nos. 22 through 29) were used of the conventional method and using those shown in Table 4 electrically conductive glass sealing materials for forming the electrically conductive glass seals 4 and 6 and one Resistance glass sealing material produced by adding 0.3 parts by weight of PVA to a mixture of 80.5 parts by weight borosilicate glass powders, 4.5 parts by weight carbon powders, 5 parts by weight Obtained silicon carbide powders, 5 parts by weight of titanium carbide powders and 5 parts by weight of boron carbide powders became. The average VCR of these resistor glass seal spark plugs is given in Table 4.

Table 4

Sample Composition of the electrically conductive glass sealing material No. (Parts by weight)

Carbon copper glass brass

iron

nickel

VCR

(ppm / V)

22 23 24 25 26 27 28 29

5 10 15 20

10 10 10

45 40 25 20 50

50 50 60 60 50 50 50 50

40

40

-51 -44 -53 -55 -83 -46 -46 -47

Forty resistance glass seal spark plugs for each sample (Sample Nos. 30 to 38) were used of the conventional method and using an electrically conductive glass sealing material from a mixture of 10 parts by weight of carbon powders, 50 parts by weight of copper powders and 40 Parts by weight of glass powders and the resistance glass sealing materials listed in Table 5 manufactured. The average VCA of these resistor glass seal spark plugs is shown in Table 5 specified.

Table 5

sample Composition of the resistance glass sealing material (parts by weight) silicon titanium boron Glass Aluminum-silicon dioxide VCR No. Coals carbide carbide carbide oxide Zirconium (ppm / V) material 10 5 80 10 - dioxide 30th 5.0 10 5 _ 79.7 20th - - -47 31 5.3 5 5 5 79.4 30th 20th - -48 32 5.6 10 5 - 79.6 - 10 - -50 33 5.4 10 5 - 79.8 - 5 - -44 34 5.2 3 5 2 85.1 - 5 - -43 35 4.9 3 3 15th 733 - - -48 36 5.7 - -67

5.1 5.3

79.9 79.7

10
20th

-51 -52

As shown in Tables 1 to 5, the VCA value becomes when the electrically conductive glass sealing materials Carbon added is lower than the known values.

Forty resistance glass seal spark plugs for each sample (Sample Nos. 61 to 65) were used of the conventional method and using those shown in Table 6 electrically conductive glass sealing materials and a resistive glass sealing material produced by Addition of 03 parts by weight of PVA to a mixture of 85.7 parts by weight of borosilicate glass powders, 43 Parts by weight of carbon powders and 10 parts by weight of silicon carbide powders was obtained. The average VCÄ value of these resistance glass seal spark plugs is shown in Table 6. As the

Table 6 shows, the VCA is that containing carbon in amounts of 2 parts by weight or more Sample No. 61 and 62 lower than -70 ppm / V.

Table 6

Sample composition of the electrically conductive VCR (ppm / V)

No. Glass sealing material (parts by weight)

Carbon copper glass

61 2.5 50 47.5 -63 62 2.0 50 48 -67 63 1.7 50 48.3 -71 64 1.5 50 48.5 -73 65 1.0 50 49 -74

sample Composition of the electrically conductive Change of the No. Glass sealing material (parts by weight) Resistance value according to Carbon copper glass Ignition duration test (0/0)

66 20th 40 40 128 67 23 40 37 140 68 26th 40 34 170 69 30th 40 30th 230

Forty resistance glass seal spark plugs for each sample (Sample Nos. 66 to 69) were used of the conventional method and using those shown in Table 7 electrically conductive glass sealing materials and a resistive glass sealing material produced by Addition of 0.3 parts by weight of PVA to a mixture of 85.6 parts by weight of borosilicate glass powders, 4.4 Ge-20 parts by weight of carbon powders and 10 parts by weight of silicon carbide powders. The changes the resistance values after the ignition duration test are given in Table 7. As Table 7 shows, is the change in the resistance value of carbon in an amount of 20 parts by weight (or less) containing sample no. 66 relatively low (128%), but the changes in the other samples are undesirably high.

Table 7

I As shown in Tables 6 and 7, if the amount of carbon in the electrically conductive

II glass sealing material is less than 2 parts by weight per 100 parts by weight of the material, the effect of IF ₄₀ lowering the VCR value to be very low, while the changes of the resistance values, when the coal-H amount of substance more than 20 parts by weight per 100 parts by weight of the material , after the ignition duration attempt § become undesirably high. Therefore, the amount of carbon in the electrically conductive glass sealing material is to be selected in the Ssj range of 2 to 20 parts by weight per 100 parts by weight of the material. The particle size of the carbon should preferably be 10 μm or less, even better 1 μm or less.

§J 45 Concerning the electrically conductive glass sealing material used metal powder, so was in the

E ;; above examples copper powder used, but other metal powders, preferably iron,

ϊ |. Brass and nickel powders can be used either alone or as a mixture thereof. The particle size

,1? the metal powder is preferably such that it can pass through a sieve with a mesh size of 0.074 mm.

||| 10 μm or less are even better. In addition, silver, gold, platinum and similar powders can also be used as metal powder

1 | ₅₀ ver can be used in the electrically conductive glass sealing material, but they are expensive. It is not

It is advantageous to use tungsten, molybdenum and palladium powders, as they cause considerable changes in the resistance

Il cause stability values after the ignition duration test.

fe The amount of glass in the electrically conductive glass sealing material is preferably in the range of 35 to 65

_f j ¥ parts by weight per 100 parts by weight of the material. When the amount of glass is less than 35 parts by weight, can

j £. ₅₅ the in F i g. 1 slightly loosen the screw head 1 shown, while with a glass quantity higher than 65 weight

If there are unwanted deviations in the resistance values.

^l j§ The amount of glass in the resistor glass material is preferably in the range of 45 to 94 parts by weight per 100

per * parts by weight of the material. When the amount of glass is less than 45 parts by weight, the airtightness becomes the

H resistance glass sealing spark plugs worse, while with a higher amount of glass than 94 parts by weight

I ₆₀ unwanted changes in the resistance values occur.

|| As mentioned above, the resistor glass seal spark plugs according to the invention have low VCR

S values and, as a result, a low interference field strength, as indicated by the solid curve 14 in FIG

I is illustrated in comparison with conventional resistive glass seal spark plugs.

if 65 1 sheet of drawings

Claims (2)

Patent claims: 1. Spark plug with resistance glass seal, between which the high voltage supply is used Terminal screw and the central electrode of the spark plug electrically connected to it a first the connecting screw is electrically conductive and contains metal powder and glass, then followed by a carbon powder, electrically insulating powder and / or resistor powder and Resistance glass seal containing glass and then a second one on the center electrode adjacent, electrically conductive, metal powder and glass containing glass seal are provided, d a through characterized in that the first electrically conductive glass seal (4) or both the first ίο electrically conductive glass seal (4) or both the first and the second electrically conductive glass seal (4,6) also contain carbon. 2. The spark plug of claim 1, wherein the first or each electrically conductive glass seal is 25-60 % By weight of one or more metals and 35 to 65% by weight of glass, characterized in that the the first or each electrically conductive glass seal (4; 4, 6) has 2 to 20% by weight of carbon.